ITEX Circumarctic CO2 Flux Survey: CO2 Flux Measurements

Data File Structure

CO2_flux_measurements.xls

Each row of data represents a single net CO2 flux measurement (net ecosystem productivity, NEP) with associated light level, air temperature, NDVI, etc. in columns. The sorting variables allow each flux measurement to be identified within a year, site, plot, and light response curve (light curves consist of 8 to 10 flux measurements and each curve has its own unique identifier). Negative NEP represents CO2 uptake by vegetation; positive NEP represents loss of CO2 to the atmosphere. Ecosystem respiration (Re) is NEP measured in the dark. Gross primary productivity (GPP) is calculated as Re - NEP. Re and GPP are given as absolute values.

Variable Description
YEAR Year of measurement
DATE Date of data collection
SITE Abisko, Toolik, or Svalbard
GROUP STEPPS, Latnjajaure, or Paddus (Abisko, Sweden); Imnavait or Toolik Lake (Alaska, USA); airport, babbling brook, Bjorndalen, Callaghan, fragile site, happy valley, ocean view, river bed, Svalsat, or salt marsh (Svalbard, Norway)
PLOT Individual plot identifier
TREAT Controlled or fertilized annually (with N and P)
PHASE Measurement series (round of measurements within each year)
CURVE ID Light curve identifier
OBSNUM Individual flux measurement identifier
START TIME Time of start of light curve
SHADELEVEL L=ambient light, S1=1 shade cloth, S2=2 shade cloths, S3=3 shade cloths, D=dark
PRESSURE Average barometric pressure (0.1 kPa)
AIRTEMP Average chamber air temperature (0.1 °C)
CO2 Average chamber CO2 concentration (0.1 ppm)
H2O Average chamber H2 concentration (0.1 mmol*mol-1)
PAR Average incident photosynthetic active radiation (µmol photons m-2*s-1)
PAR RANGE Range of incident PAR values recorded during measurement (µmol photons m-2*s-1)
NDVI Normalized difference vegetation index (0.01 dimensionless)
NEP Net ecosystem productivity (0.1 µmol C m-2*s-1)
H2Oflux H2O flux (0.1 mmol H2O m-2*s-1)
RE Ecosystem respiration (0.1 mol C m-2*s-1)
GEP Gross ecosystem productivity (0.1 µmol C m-2*s-1)

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